1. Field of the Invention
The present invention relates to an improved underground water retention/detention system comprised of a roof supported by stabilized porous perimeter structures constructed with open graded aggregate and columns/piers enclosed in a liner system.
2. Description of the Prior Art
Water retention/detention systems store and release water at a controlled rate in accordance with increasingly stringent environmental requirements. Storm water retention/detention systems have become standard features on site development projects where buildings, roads and parking lots have limited the site's ability to absorb water. In response, many state and municipal agencies have limited the rate at which storm water can be discharged into local streams. A detention pond is often constructed at new developments to store and release water at a designated rate. Where land is valuable or where space is limited or where other concerns are present retention/detention systems are constructed underground. See, for example, U.S. Pat. Nos. 6,796,325, 4,620,817 and 6,702,517.
In accordance with prior procedures, engineers have provided various means for directing storm water into the earth for storage and disposal. For example crushed stone pits have been employed, frequently with perforated pipes therein. Various shaped or molded structures made of concrete, steel or plastic have been employed.
Large diameter pipes have traditionally been used to construct below grade retention/detention systems. Typically these systems involve a series of parallel pipes placed on a prepared bed at the bottom of an excavation. The pipes must be adequately spaced, backfilled with a select soil and covered to a minimum height.
As a result of the backfill requirements and the limited capacity of pipes, these systems often require more area than is desired or available. As an alternative to traditional underground retention/detention systems the present invention proposes to decrease the required footprint and/or provide an economical alternative among other advantages.
Prior systems have taken up large areas and/or have involved the use of elaborate and costly components. Improved underground retention/detention systems remain an important objective.